Known tuning-fork type crystal resonator plates include a tuning-fork type crystal resonator plate made up of a base portion and two leg portions protruding from the base portion (see, for example, Patent Document 1). Such a tuning-fork type crystal resonator plate includes a pair of driving electrodes having different potentials formed on the two leg portions. A turning-fork type crystal resonator device is made by hermetically sealing the tuning-fork type crystal resonator plate within an internal space of a main body casing made up of a base and a lid (see, for example, Patent Document 1). The tuning-fork type crystal resonator plate includes grooves formed in the leg portions so that bank portions are formed on the leg portions. The CI value can be reduced by the grooves. When the width of the groove is increased, the width of the bank portion is decreased and electrolytic efficiency is improved, thus the CI value can be further reduced. However, in order to vibrate the leg portion, the minimum width of the bank portion should be ensured. Thus, the widths of the grooves and the bank portions are limited according to the size of the leg portion, which means that the reduction of the CI value by increasing the width of the grooves is also limited. Also, conventionally, a side surface of the leg portion has a pointed protrusion due to crystal anisotropic etching. Such a protrusion causes variation in the distance in the width direction of the leg portion between an electrode on an internal surface of the groove and an electrode on the side surface of the leg portion, which decreasing vibration efficiency.